How to repair dry rot on ends of exposed beams?

cathyinbothellSeptember 12, 2009

My husband and I own a small A frame 30 year old cabin that is close to the water. The cabin is a typical A frame, with huge beams that support the roof and go from the inside and extend outside a few feet. We started noticing some dry rot at the end of the exposed outside beams last year, (these are about four feet off the ground) and this year it has really progressed. We can stick a screw driver in the end up to six or more inches. Should we cut the neds of these beams off and attach new wood somehow? Or should we fill the rotted ends with something and cap them or are there other options? Any advice would be appreciated,


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I am no expert, just a DIY. I had some spots outside with some rot (wet rot and some dry rot) I repaired. I removed all the bad wood and let it dry for at least a few good hot dry days so any moisture was gone. I think I also sprayed it with some bleach to kill any mold spores, I think you can use borax solution also. Applied wood hardener (minwax makes some)it makes the wood harder if it is a bit soft. Then used wood filler (not wood putty) It drys pretty hard. Then I primed and painted it. Its been a few years since the repair and it seems to be holding up. I probably should have sanding it a bit more where I used it but it's not in a area really seen.

    Bookmark   September 13, 2009 at 9:10AM
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Do these ends stick out beyond the roof line so that they are exposed directly to the elements? And is any of the damaged stuff structural (meaning the rotted area is directly supporting something)?

    Bookmark   September 13, 2009 at 1:34PM
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Can't say without a photo.

    Bookmark   September 13, 2009 at 5:51PM
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Whatever your solution, be advised that dry rot needs complete removal lest it begin anew on any wood attachment.
I personally do not know whether bleach or mildewcide is effective. Chlorine/hypochlorite has destructive properties in:re wood besides most other materials.
As Macv says, hard to say without a photo, but presumably the tails though part of the load bearing member would be less loaded and amenable to splicing.

    Bookmark   September 14, 2009 at 6:37AM
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I agree with previous post - after applying wood hardner ( I use the Minwax) let it dry for a day. As for a filler, I use regular Bondo. I then sand smooth and prime and paint.

    Bookmark   September 16, 2009 at 1:39PM
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In general, it's best to remove as much damaged wood as possible, and replace it with a paste EPOXY, like PC-Woody (strong, wood-colored), or PC-7 (very strong, but gray), or PC-Concrete or Simpson Strong-Tie ET/SET anchoring epoxy (KILLER strong!... but concrete gray color).

Beware of Bondo and similar auto body fillers. They are made to be sealed with paint, and will soak up a LOT of water if they are left unpainted.

A bleach solution WILL kill everything IT CAN GET TO in wood, but TSP (tri-sodium phosphate) will enhance the process by making the solution "wetter", and thus able to penetrate deeper, and GET TO more rot. Most brands of TSP will have recommended proportions of water, bleach, and TSP on the box. TSP is sometimes marketed as "Deck Cleaner" in order to boost the price of this simple chemical.

As for the Minwax wood hardener, it might be OK, in some apps, but it's pretty lame compared to the LOW-VISCOSITY EPOXY RESINS designed for the task of soaking into wood, consolidating the loose stuff, and then curing into... epoxy. ;')

There's "PC Rot-Terminator" from PC Products, available on, and "RotFix" from System Three, available at Woodcraft stores. It's not cheap.

With any epoxy product, THOROUGH mixing of the 2 parts is essential to success.

Here is a link that might be useful: Some useful info/video on rot and products...

    Bookmark   September 17, 2009 at 12:12AM
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